问题
单项选择题
The ratio of the work done by the machine（）the work done on it is called the efficiency of the machine.
A.against
B.with
C.to
D.for
答案
参考答案：C
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The ratio of the work done by the machine（）the work done on it is called the efficiency of the machine.
A.against
B.with
C.to
D.for
参考答案：C